/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.util;

import java.io.ByteArrayOutputStream;

/**
 * Library of utility methods useful in dealing with converting byte arrays
 * to and from strings of hexadecimal digits.
 *
 * Note: this package has been stripped of its localization capabilities,
 * to lessen library dependencies and increase portability.
 * - ARJ, 4/04
 *
 * @author Craig R. McClanahan
 * @since 2.3
 */

public final class HexUtils
{
    // Code from Ajp11, from Apache's JServ

    // Table for HEX to DEC byte translation
    static final int[] DEC =
    {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        00, 01, 02, 03, 04, 05, 06, 07,  8,  9, -1, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    };

    /**
     * Convert a String of hexadecimal digits into the corresponding
     * byte array by encoding each two hexadecimal digits as a byte.
     *
     * @param digits Hexadecimal digits representation
     *
     * @exception IllegalArgumentException if an invalid hexadecimal digit
     *  is found, or the input string contains an odd number of hexadecimal
     *  digits
     */
    public static byte[] convert(String digits)
    {

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        for (int i = 0; i < digits.length(); i += 2)
        {
            char c1 = digits.charAt(i);
            if ((i+1) >= digits.length())
                throw new IllegalArgumentException
                    ("Odd number of hexadecimal digits");
            char c2 = digits.charAt(i + 1);
            byte b = 0;
            if ((c1 >= '0') && (c1 <= '9'))
                b += (c1 - '0') * 16;
            else if ((c1 >= 'a') && (c1 <= 'f'))
                b += (c1 - 'a' + 10) * 16;
            else if ((c1 >= 'A') && (c1 <= 'F'))
                b += (c1 - 'A' + 10) * 16;
            else
                throw new IllegalArgumentException
                    ("Bad hexadecimal digit");
            if ((c2 >= '0') && (c2 <= '9'))
                b += c2 - '0';
            else if ((c2 >= 'a') && (c2 <= 'f'))
                b += c2 - 'a' + 10;
            else if ((c2 >= 'A') && (c2 <= 'F'))
                b += c2 - 'A' + 10;
            else
                throw new IllegalArgumentException
                    ("Bad hexadecimal digit");
            baos.write(b);
        }
        return baos.toByteArray();

    }


    /**
     * Convert a byte array into a printable format containing a
     * String of hexadecimal digit characters (two per byte).
     *
     * @param bytes Byte array representation
     */
    public static String convert(byte[] bytes)
    {

        StringBuffer sb = new StringBuffer(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++)
        {
            sb.append(convertDigit(bytes[i] >> 4));
            sb.append(convertDigit(bytes[i] & 0x0f));
        }
        return sb.toString();

    }

    /**
     * Convert 4 hex digits to an int, and return the number of converted
     * bytes.
     *
     * @param hex Byte array containing exactly four hexadecimal digits
     *
     * @exception IllegalArgumentException if an invalid hexadecimal digit
     *  is included
     */
    public static int convert2Int( byte[] hex )
    {
        // Code from Ajp11, from Apache's JServ

        // assert b.length==4
        // assert valid data
        int len;
        if(hex.length < 4 ) return 0;
        if( DEC[hex[0]]<0 )
            throw new IllegalArgumentException("Bad hexadecimal digit");
        len = DEC[hex[0]];
        len = len << 4;
        if( DEC[hex[1]]<0 )
            throw new IllegalArgumentException("Bad hexadecimal digit");
        len += DEC[hex[1]];
        len = len << 4;
        if( DEC[hex[2]]<0 )
            throw new IllegalArgumentException("Bad hexadecimal digit");
        len += DEC[hex[2]];
        len = len << 4;
        if( DEC[hex[3]]<0 )
            throw new IllegalArgumentException("Bad hexadecimal digit");
        len += DEC[hex[3]];
        return len;
    }

    /**
     * [Private] Convert the specified value (0 .. 15) to the corresponding
     * hexadecimal digit.
     *
     * @param value Value to be converted
     */
    private static char convertDigit(int value)
    {

        value &= 0x0f;
        if (value >= 10)
        {
            return (char) (value - 10 + 'a');
        }
        return (char) (value + '0');
    }

}
